The success of a colonoscopy is closely linked to good bowel preparation, with poor bowel prep often resulting in missed precancerous lesions, according to new consensus guidelines released by the US Multi-Society Task force on Colorectal Cancer. Additionally, poor bowel cleansing can result in increased costs related to early repeat procedures. Up to 20% to 25% of all colonoscopies are reported to have an inadequate bowel preparation.

“When prescribing bowel preparation for their patients, health care professionals need to be aware of medical factors that increase the risk of inadequate preparation, as well as nonmedical factors that may predict poor compliance with instructions,” according to lead author David A. Johnson, MD, professor of internal medicine and chief of the division of gastroenterology, Eastern Virginia Medical School, Norfolk. “Gastroenterologists should use this information when determining whether to use a more effective or aggressive bowel preparation regimen, as well as the level of patient education needed about the prep.”

Adequate preparation is defined as sufficient to allow detection of polyps greater than 5 mm. Such level of cleansing allows for screening and surveillance interval recommendations that comply with guideline intervals appropriate to the findings of the examination. This benchmark should be achieved in 85% or more of all examinations on a per-physician basis.

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Inadequate preparation of the colon is associated with reduced adenoma detection rates. Preliminary assessment of prep quality should be made. If the indication is screening or surveillance and the preparation is inadequate to allow detection of polyps greater than 5 mm, the procedure should be either terminated and rescheduled or additional bowel cleansing strategies should be attempted to allow continuation of the procedure that day.

If the colonoscopy is complete to the cecum and the preparation is ultimately deemed inadequate, then the examination should be repeated within 1 year, generally with a more aggressive preparation regimen; intervals shorter than 1 year are indicated when advanced neoplasia is detected and there is inadequate preparation.

If the preparation is deemed adequate and the colonoscopy is completed, then the guideline recommendations for screening or surveillance should be followed.

Use of a split-dose bowel cleansing regimen is strongly recommended for elective colonoscopy, meaning roughly half of the bowel cleansing dose is given the day of the colonoscopy. The second dose of split preparation ideally should begin 4 to 6 hours before the time of colonoscopy with completion of the last dose at least 2 hours before the procedure time. During a split-dose bowel cleansing regimen, diet recommendations can include either low-residue or full liquids until the evening on the day before colonoscopy. A same-day regimen is an acceptable alternative to split dosing, especially for patients undergoing an afternoon examination.

Health care professionals should provide both oral and written patient education instructions for all components of the colonoscopy preparation and emphasize the importance of compliance. The physician performing the colonoscopy should ensure that appropriate support and process measures are in place for patients to achieve adequate colonoscopy preparation quality.

This consensus statement was published in Gastroenterology (2014; doi:10.1053/j.gastro.2014.07.002).